During the study we recorded narrow margins between zooplankton distribution and the ecological characteristics of water in Bokakotorska Bay (Adriatic sea, Montenegro). Various species show different vulnerability to environment quality. Some are defined as indicators, with low tolerance for the ecological variation of environment, and their distribution is limited to the particular type of water masses within the sea. The limiting factors are different for various species, and their indicator status is determined by their distribution. The indicator type, based on monitoring of particular species, may define a biotope, with the help of statistical analyses that identify the main time and spacial behavior patterns of a species, and my allow future ecosystem changes to be anticipated. In this paper we paid particular attention to the indicator species Oithona nana (Giesbrecht).

In this paper the results of zooplankton investigations (and its dominant group Copepoda) were presented from the part of the Boka Kotorska Bay with more intensive circulation with the open sea, from summer of 2005. Some results from the open South Adriatic were given, too - from the frontal zone exposed to anthropogenic eutrophication of Bojana and Drim rivers, and the impact of oligotrophic South Adriatic, simultaneously.

In this paper, results of phytoplankton investigations were performed in June 2005. The investigated positions are located near the entrance of Boka Kotorska Bay: two positions in the outer part (Zanjica and Mamula island) and two positions in the inner part of the Bay (Njivice and Tivat bay). In this area the influences of the open sea and the land are expressed to the phytoplankton community. As a consequence of that quantities of phytoplankton are lower in the outer part and higher in the inner part. The most dominant species is diatom Pseudo-nitzschia delicatissima which is very frequent in the eutrophic area.

Oil spill phenomena occur very often in the Boka Aquatorium. By studying the occurrence of oil stain on the sea surface the analyses of the Boka Bay pollution is represented in this document. Also represented is an evaluation or stimulation of expert opinion in a case of oil spill occurrence, in relation to the air temperature with the obvious consequences of carbon hydrogen appearance/presence.

Investigation of the nutrients and chlorophyll a concentrations, as indicators of trophic level, in the period from September 2003 to August 2004 in three sampling locations in the inner part of Boka Kotorska Bay varied widely. Nitrate concentration ranged from 0.0 to 2.42 mg/l at the surface and from 0.02 to 3.88 mg/l at the bottom, nitrate concentration from 0.02 to 0.21 mg/l at the surface and from 0.01 to 0.6 mg/l at the bottom, phosphate concentration from 0.03 to 0.18 mg/l at the surface and from 0.01 to 0.22 mg/l at the bottom, silicate concentration from 0.0 to 1.42 mg/l at the surface and 0.45 mg/l at the bottom respectively. Value of phytoplankton biomass, as represented by chlorophyll a, ranged from 1.02 to 8.68 mg/cubic meter and from 0.49 to 5.23 mg/cubic meter at the bottom. According to the UNEP criteria during the investigated period it can be concluded that the area in question is mesotrophic with the exception of December when it is eutrophic.